The present invention relates to a system for removably and mechanically locking on a rotary drive shaft a sleeve which is designed to be slipped axially over said shaft and to be driven in rotation by said shaft, especially using splines.
In general, rotational drive to power take-off constant-velocity joints is via a conventional splined coupling, while the axial positioning of the sleeve of the joint on the shaft is achieved using a circlip or snap ring housed in complementary grooves formed respectively on the external surface of the shaft and on the internal surface of the sleeve; the constant-velocity joint which is immersed in lubricant, is hermetically sealed and the end of the shaft is inaccessible once the joint has been fitted.
The drawbacks of this type of fastening are known.
The clearances required between internal and external splines for assembling allow slight rotational and flexural oscillations of the joint on the shaft when the direction of torque is reversed as well as at low continuous torques because of vibration of the power unit. This may result in noise which is detrimental to comfort and in contact corrosion. This type of coupling cannot therefore be used for transmissions that run at a high rotational speed.
This type of fastening is incapable of axially locking the inner race of the output rolling bearing of the shaft in question, which means that this race has to be mounted on the shaft with a very tight diametral fit with small tolerances.
The joint is removed by pulling forcefully on the transmission in order to overcome the resistance of the snap ring and the friction. The snap ring therefore needs to be flexible enough that it moves aside radially during removal, but rigid enough to hold the joint in place during use. This particular feature involves the profile of the grooves being produced with great care.
Furthermore, upon assembly, it is impossible to check unequivocally that the snap ring has been fitted correctly in these housings, and therefore that assembly is reliable.
A conventional solution that allows these drawbacks to be overcome consists in inserting a flanged sleeve between the shaft and the constant-velocity joint, as depicted in FIG. 1. First of all, the sleeve 1, which has a flange 6, is fastened to the splined shaft 2 using a nut 3 which axially locks the sleeve 1 against the inner race 4 of the output bearing 5 through which the shaft 2 protrudes from the casing 7. The flange 6 is then fastened to the collar 8 of the constant-velocity joint 9 closed by the plug 10, by means of the bolts 11.
This assembly, which is satisfactory from the point of view of mechanical quality of the coupling, does, however, have the following drawbacks.
It appreciably increases the cost of machining for the coupling as a result of the addition of the flange 6, which is a bulky mechanical component, and increases the cost of assembly.
The diametral bulk of the constant-velocity joint and of the coupling is increased.
The overhang from the center of articulation of the joint relative to the bearing that guides the shaft is appreciably increased.
The mass of the connection also is increased.